1. Field of the Invention
The present invention relates to a plasma display panel in which a fluorescent layer emits light to form an image by receiving ultraviolet light generated during gas discharge.
2. Description of the Related Art
A plasma display panel has been widely known as a flat type display panel, equivalent in quality to a cathode ray tube, due to its capacity to display large amounts of data, it's a wide viewing angle, and superior brightness and contrast features.
In general, the plasma display panel is divided into a DC plasma display panel and an AC plasma display panel according to its operation principle. The DC plasma display panel has all electrodes exposed to a discharge space in which charges move directly between opposite electrodes. While, in the AC plasma display panel, at least one electrode is coated with a dielectric and discharge is generated by the electric field of wall-charges.
Also, the plasma display panel is divided into an opposed discharge type and a surface discharge type according to the composition of electrodes. In the opposed discharge type plasma display panel, an address electrode and a scanning electrode are installed at each unit pixel to face each other and an addressing discharge for selectively discharging a desired pixel and a sustaining discharge for sustaining the addressing discharge are generated between the two opposed electrodes.
In the surface discharge type plasma display panel, however, each unit pixel is provided by a scanning electrode and a common electrode opposing an address electrode. Addressing and sustaining discharges are generated between the address electrode and the scanning electrode, and the scanning electrode and the common electrode, respectively.
Ultraviolet light generated during discharge in the plasma display panel allows a fluorescent layer disposed in a discharge space to emit light, so that an image is formed.
FIG. 1 shows an example of a conventional plasma display panel.
As shown in the drawing, the conventional plasma display panel includes a substrate 10, a first electrode 11 formed on the substrate 10, a dielectric layer 12 coated over the first electrode 11 and the substrate 10, a partition 13 formed on the dielectric layer 12 for defining a discharge cell and preventing cross talk between the discharge cells, and a fluorescent layer 14 formed in a predetermined pattern inside the discharge space between the partitions 13.
A transparent front substrate 20 is installed atop the partition 13. Second and third electrodes 21 and 22 are formed on the lower surface of the front substrate 20 to be perpendicular to the direction of the first electrode 11. A dielectric layer 23 and a protective layer 24 are coated in sequence on the lower surfaces of the second and third electrodes 21 and 22 and the front substrate 20.
As a predetermined voltage is applied to each electrode, charges are accumulated in the dielectric layer 12. The accumulated charges trigger a discharge between the first and second electrodes 11 and 21 so that charged particles are formed on the lower surface of the dielectric layer 23 of the front substrate 16. When a predetermined voltage is applied to the second and third electrodes 21 and 22 in such a state, a sustaining discharge is generated. Thus, a plasma is formed in a charged gas layer in the discharge space. In the plasma, ultraviolet light is emitted and the fluorescent layer 14 excited by the ultraviolet light emits light.
During the operation of the plasma display panel as above, part of the ultraviolet light emitted by the gas discharge is absorbed by the front substrate 20 and the partition 13 where the fluorescent layer 14 is not formed. Also, part of the light emitted by the fluorescent layer 14 is dissipated into the dielectric layer 12 and the substrate 10 under the fluorescent layer 14, which does not affect brightness.
Plasma display panels introduced to solve the above problems are disclosed in U.S. Pat. No. 5,182,489 and Japanese Patent No. hey 5-80390.
FIG. 2 shows an example of a plasma display panel described in the above documents. Here, the same reference numerals as those in FIG. 1 indicate the same members. As shown in the drawing, a visual-ray reflection layer 16 having an upper surface processed with an insulation material is formed between a substrate 10 and a dielectric layer 12. The reflection layer 16 reflects the light proceeding toward the substrate 10 from a phosphor layer 14, toward a front substrate 20, to thus increase brightness. However, since the reflection layer 16 reflects only the visual ray emitted by the phosphor layer 14 and has a limit in reflecting ultraviolet light generated during gas discharge, a considerable improvement in the brightness cannot be expected. In particular, since the transmittance of the visual light of the phosphor layer 14 is extremely low, there is a limit to improving the brightness using the reflection layer 16.